eMaker Huxley modified Z endstop

This is my first attempt at a modification to my printer and I'm pretty pleased with it. I love printing with my Huxley - http://www.thingiverse.com/thing:5631 - but one of the frustrations is the major impact on print quality with even minor variation in the height of the nozzle when printing the first layer. I use spark plug feeler gauges to set the height to 0.2 mm for a 0.3 mm layer height but I found the method of adjusting the Z-endstop didn't give me the level of control I wanted.
So I r